Generation and characterization of monoclonal antibodies specific for the human IFN-gamma receptor

Purified preparations of the human IFN-gamma R derived from placental membranes were used to produce receptor-specific murine mAb. Supernatants from growth-positive wells were screened for their ability to block binding of 125I-IFN-gamma to human placental membranes. Ten inhibitory cultures were identified. Two of these (GIR-208 and GIR-301) abrogated all binding of radioligand to either intact placental membranes or soluble, purified IFN-gamma R. Three others (GIR-72, 76 and 94) showed moderate blocking activity (65, 59, and 49%, respectively) whereas the remaining five (GIR-57, 67, 83, 109, and 153) blocked binding to a low but significant extent (20 to 40%). Specificity experiments demonstrated that the antibodies reacted with the receptor and not the ligand (IFN-gamma). None of the antibodies reacted with IFN-gamma by ELISA. Moreover, GIR-208 and GIR-301, but not isotype-matched controls, identified the receptor by Western blot analysis. GIR-208 and GIR-301 also completely abrogated binding of 125I-IFN-gamma to either mononuclear phagocytes (U937) or human fibroblasts (WISH). Competition experiments revealed that GIR-208 and GIR-301 recognized similar epitopes on the IFN-gamma R and that these (or this) epitopes were identical to or linked to the ligand binding site of the receptor. In addition, both antibodies inhibited development of IFN-gamma-dependent anti-viral activity in WISH cells in a dose-dependent fashion. These data thus indicate that the IFN-gamma R expressed on human placental cells, mononuclear phagocytes, and fibroblasts are similar.

Generation and characterization of monoclonal antibodies specific for the human IFN-gamma receptor

Purified preparations of the human IFN-gamma R derived from placental membranes were used to produce receptor-specific murine mAb. Supernatants from growth-positive wells were screened for their ability to block binding of 125I-IFN-gamma to human placental membranes. Ten inhibitory cultures were identified. Two of these (GIR-208 and GIR-301) abrogated all binding of radioligand to either intact placental membranes or soluble, purified IFN-gamma R. Three others (GIR-72, 76 and 94) showed moderate blocking activity (65, 59, and 49%, respectively) whereas the remaining five (GIR-57, 67, 83, 109, and 153) blocked binding to a low but significant extent (20 to 40%). Specificity experiments demonstrated that the antibodies reacted with the receptor and not the ligand (IFN-gamma). None of the antibodies reacted with IFN-gamma by ELISA. Moreover, GIR-208 and GIR-301, but not isotype-matched controls, identified the receptor by Western blot analysis. GIR-208 and GIR-301 also completely abrogated binding of 125I-IFN-gamma to either mononuclear phagocytes (U937) or human fibroblasts (WISH). Competition experiments revealed that GIR-208 and GIR-301 recognized similar epitopes on the IFN-gamma R and that these (or this) epitopes were identical to or linked to the ligand binding site of the receptor. In addition, both antibodies inhibited development of IFN-gamma-dependent anti-viral activity in WISH cells in a dose-dependent fashion. These data thus indicate that the IFN-gamma R expressed on human placental cells, mononuclear phagocytes, and fibroblasts are similar.

Reduced receptor binding by a human interferon-gamma fragment lacking 11 carboxyl-terminal amino acids

Treatment of recombinant human interferon-gamma (IFN-gamma) with either 1) the arginine-specific proteases clostripain or submaxillaris protease or 2) the broadly specific enzyme pronase produced a stable fragment with m.w. of 15,500. Structural analysis showed that the cleavage occurred between residues 129 and 130 and thus produced a fragment lacking only 11 carboxyl-terminal amino acids. The fragmented and untreated molecules showed identical amino-terminal amino acid sequences and were equally reactive with either polyclonal or monoclonal anti-IFN-gamma. IFN-gamma lacking carboxyl-terminal amino acids displayed a 1000- to 2000-fold reduction in its capacity to bind to cellular IFN-gamma receptors at 4 degrees C. Functionally the fragment showed a 50-fold reduction in its ability to induce antiviral activity in fibroblasts and a 10-fold reduction in its ability to induce Fc receptors on the human histiocytic lymphoma cell line U937. These results thus suggest that the carboxyl terminus of human IFN-gamma contributes significantly to the formation of the receptor-binding site of the molecule.

Reduced receptor binding by a human interferon-gamma fragment lacking 11 carboxyl-terminal amino acids

Treatment of recombinant human interferon-gamma (IFN-gamma) with either 1) the arginine-specific proteases clostripain or submaxillaris protease or 2) the broadly specific enzyme pronase produced a stable fragment with m.w. of 15,500. Structural analysis showed that the cleavage occurred between residues 129 and 130 and thus produced a fragment lacking only 11 carboxyl-terminal amino acids. The fragmented and untreated molecules showed identical amino-terminal amino acid sequences and were equally reactive with either polyclonal or monoclonal anti-IFN-gamma. IFN-gamma lacking carboxyl-terminal amino acids displayed a 1000- to 2000-fold reduction in its capacity to bind to cellular IFN-gamma receptors at 4 degrees C. Functionally the fragment showed a 50-fold reduction in its ability to induce antiviral activity in fibroblasts and a 10-fold reduction in its ability to induce Fc receptors on the human histiocytic lymphoma cell line U937. These results thus suggest that the carboxyl terminus of human IFN-gamma contributes significantly to the formation of the receptor-binding site of the molecule.

Loss of susceptibility to complement lysis in Entamoeba histolytica HM1 by treatment with human serum

Entamoeba histolytica HM1, exposed to a series of treatment with normal human serum (NHS), progressively lost susceptibility to complement lysis. Trophozoites were incubated daily with unheated or heat-inactivated NHS for 2 hr at 36 degrees, starting with 10% v/v serum and increasing by 5% every 3 days up to 40% NHS. Resistance to complement lysis was also obtained with two different HM1 clones but not with the low virulent strain HK9. Induction of resistance dependent on the number of NHS treatments, with a maximal 50% reduction occurring after 11 treatments. Susceptibility to complement-dependent lysis was regained 6 weeks after serum treatments were terminated, suggesting that resistance to lysis was an acquired rather than a genetic property.

Overdose of cyclobenzaprine, the tricyclic muscle relaxant

A case of cyclobenzaprine (Flexeril) overdose in a 31-year-old woman is presented. The treatment rendered was analogous to treatment protocols implemented for tricyclic overdose. A review of the pharmacology of cyclobenzaprine, as well as the management of patients who overdose on this drug, is presented.

Activation of the alternative and classical complement pathways by Entamoeba histolytica

Entamoeba histolytica HM1 supported the activation of human alternative and classical complement pathways in the absence of ameba-reactive antibodies. Nonimmune serum depleted of C1q and factor D (NHS s C1q + D) and reconstituted with C1q was able to specifically deposit C3b onto trophozoites and produce lysis. This activity was not modified by the absorption of serum on E. histolytica. Serum depleted of factor B allowed C3b binding to amebae. Serum devoid of C4 effected only small amounts of C3 uptake. The kinetics of lysis of E. histolytica by serum in the presence of Mg-EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] (lacking classical pathway function) or by NHS s C1q + D and reconstituted with factor D was slow and only produced one-half the amount of lysis produced by NHS s C1q + D supplemented with C1q. These results indicate that the surface of the ameba can promote complement activation by the classical pathway, without the participation of specific antibodies, and that the magnitude of this activation is greater than that induced by the alternative pathway.

Clinical profiles of patients with antibodies to nuclear ribonucleoprotein

Currently there are no widely accepted criteria for the diagnosis of MCTD. In this work we attempted to define the clinical profile of a group of 68 patients with anti nRNP antibodies, detected by immunoprecipitation in 0.6% agarose. The diagnosis of each collagen vascular disease was established in every patient, who met with the strict diagnostic criteria either at clinical presentation or during the follow-up period. Twenty-eight patients had SLE, 9 had classical erosive RA, three had PSS and one had PM. The only distinctive features in the group of SLE with anti nRNP was an increased incidence of anti Sm antibodies (p less than 0.05). In the RA group there was a trend towards a high frequency of Raynaud's phenomenon and swollen hands. At clinical presentation twenty-seven patients did not fulfil enough criteria to be diagnosed of any of the well-defined collagen vascular disease. They presented an undifferentiated syndrome, characterized clinically by Raynaud's phenomenon (100%), swollen hands (88.9%) and joint symptoms (88.9%), with scarce tendency of developing severe systemic manifestations. The main laboratory abnormalities in this group were hypergammaglobulinemia, mildly increased ESR, abnormal levels of CIC, negative anti nDNA and anti Sm antibodies, and the virtual absence of hypocomplementemia. During a clinical course of 96 +/- 72.5 months only one patient evolved into another collagen disease (SLE). The clinical course in the remaining cases, was stable improving with low doses of prednisone and/or NSAID. We suggest considering this undifferentiated syndrome as a distinct entity, for which the already classical term of MCTD could be reserved.

Synthesis and release of thymidine by macrophages

An inhibitor of DNA synthesis and cell proliferation found in macrophage supernatants was subjected to further analysis. The following conclusions were drawn: a. Biochemically, the inhibitor appeared to be thymidine, judging from the migration in three different thin-layer systems and on gel filtration. b. The inhibitor was shown to be synthesized de novo by macrophage monolayers pulsed with a radiolabeled precursor of thymidine such as 14C-formate. c. The amount of inhibitor present in tissue culture fluids proved to be sufficient to block the growth of the EL-4 leukemia cell line in a manner that could be prevented with the addition of 2'-deoxycytidine. The EL-4 line was considerably more sensitive to thymidine blockade than a number of different cells tested.

Demonstration of a depressor reflex in acute cardiac tamponade

Studies from our laboratory have demonstrated the presence of a vagally mediated reflex in acute cardiac tamponade. To determine the effect of thisreflex on cardiac performance, we continuously recorded hemodynamic parameters during induction of tamponade in 16 closed-chest mongrel dogs anesthetized with alpha chloralose. The studies were done 1 to 7 days following the insertion of a catheter in the pericardial sac. With increasing pericardial volume, there was a progressive deterioration of cardiac performance, the most marked changes occuring in the late phases of cardiac tamponade...

Effect of autonomic blockade on the hemodynamic findings in acute cardiac tamponade

Twenty-three closed-chest, alpha-chloralose-anesthetized, volume-expanded, alpha- and beta-adrenergic-blockaded dogs with rate fixed by atrial pacing had 30-90 ml of saline at 37 degrees C infused into the pericardial sac a) with vagus intact, b) after vagotomy, and c) with vagus intact but with systolic pressure augmented with a balloon. A significant reduction in left ventricular (LV) systolic pressure (SP), and cardiac output (CO) occurred at a pericardial volume of 30-60 ml, when LV end-diastolic (ED) and right atrial (RA) pressures were not increased. Whereas the percentage decline of CO, LVSP, maximum negative and maximum positive dP/dt was greater in group A (vagus intact) than in group B (vagus cut), significant residual depressed performance was demonstrated only in group B. In four paced, atropinized, beta-blockaded dogs, response to tamponade was similar to that in intact dogs; vagotomy at 90 ml in these dogs resulted in a fall in CO, a rise of LVSP and a significant elevation in LVED and RA pressures. Thus, in the early phases of cardiac tamponade a sympathetic neurohumoral response supports cardiac performance while the vagus nerve exerts a myocardial protective effect. Vagal afferents appear to modulate this response.

Regulation of immunity and inflammation by mediators from macrophages

Mononuclear phagocytes secrete a number of materials into the extracellular environment. The materials secreted by phagocytes can be grouped into three categories: a) enzymes affecting extracellular proteins (collagenase, elastase, lysosomal proteases, plasminogen activators), b) materials involved in defense processes (complement proteins, interferons, lysozyme), and c) factors regulating activities of surrounding cells. The latter include lymphostimulatory molecules, a colony-stimulating factor, and inhibitors of cell growth. The conditions for secretion of the materials depend on the activity of the phagocytes. The lymphostimulatory molecules secreted by macrophages exert various effects: 1) an increase in DNA synthesis of lymphocytes, 2) a maturation of early thymocytes to mature T cells, and 3) the differentiation of some B cells to antibody-secreting cells. The mitogenic principle has been partially isolated as a protein of 15,000 to 20,000 daltons. The secretion of lymphostimulatory molecules is increased following uptake of various materials by macrophages or by addition of activated T cells to macrophage cultures.

Echocardiographic detection of fungal vegetations in Candida parasilopsis endocarditis

A case of primary Candida parasilopsis endocarditis in a heroin addict involving the aortic valve is presented. Abnormal echoes in the aortic root during diastole and in the aortic valve during systole and diastole produced by fungal vegetations were found. The demonstration of fungal vegetations by echocardiography in the absence of positive blood cultures and systemic embolization is a useful diagnostic tool which should be utilized when fungal endocarditis is suspected.

The modulation of lymphocyte functions by molecules secreted by macrophages. II. Conditions leading to increased secretion

Cultures of peritoneal exudate cells rich in macrophages were studied for the secretion of lymphostimulatory molecules. Two conditions produced increased secretion: (a) addition to the cultures of various agents that readily interacted with macrophages, such as latex particles, antibody-coated red cells, endotoxin, Listeria organisms, or Be salt; or (b) addition of activated lymphocytes. In the first case the increased activity was found during the first 24 or 48 h after uptake of the stimuli. Increased activity was found in normal or peptone-stimulated macrophages but not in macrophages after injection of endotoxin or thioglycollate. The addition of T lymphocytes from Listeria-infected mice to macrophage cultures increased greatly the activities. This increase was also produced by addition to antigen-primed T cells together with antigen. The lymphocytes by themselves did not secrete active factors. The lymphostimulatory activities were tested on thymocyte DNA synthesis and on antibody formation in vitro. The latter assay was done on spleen cells from immunized mice where one striking effect was the stimulation of differentiation to antibody-secreting cells. Some dissociation of both activities (thymocyte DNA synthesis and B-cell differentiation) was observed with selected culture fluids.

Effects of procainamide on the dispersion of recovery of excitability during coronary occlusion

In 14 mongrel dogs, refractory periods were determined in nonischemic and acutely ischemic zones of myocardium during control conditions, 15 minutes after coronary ligation, and 10 and 20 minutes after a procainamide infusion. Following coronary ligation, refractory periods in the nonischemic area remained unchanged (100.8% of control) while in the ischemia area they decreased to 88.6% of control (P less than 0.02) causing a dispersion of refractoriness of 12.2%. After the administration of procainamide, refractory periods lengthened in the nonischemic as well as in the ischemic areas but the changes were such that the temporal dispersion caused by the coronary ligation was reduced from 12.2% to 5.5% (P less than 0.01) after 10 minutes, and to 5.0% (P less than 0.02) after 20 minutes of drug infusion. It is concluded that procainamide exerts different overall effects on the nonischemic and acutely ischemic canine myocardium. It is postulated that this action may play a role in the suppression of re-entrant arrhythmias.

Sarcoidosis with incomplete bilateral bundle branch block pattern disappearing following steroid therapy: an electrophysiological study

A man with a 30-year history of pulmonary sarcoidosis, confirmed by lymph node biopsy and a positive Kveim reaction, developed an incomplete bilateral bundle branch block pattern. Cardiac catherization and angiography revealed normal pressures, hemodynamic parameters and left ventricular contractile pattern; the coronary arteries were patent. His bundle electrograms demonstrated a normal H-V interval that was not altered by atrial pacing. After four weeks of steroid therapy the electrocardiographic abnormality disappeared. However, when restudied at this time, incomplete bilateral bundle branch block pattern could be elicited on atrial pacing and with the extrastimulus technique. Other electrophysiological observations suggested the presence of an AV nodal bypass tract and demonstrated changing intraventricular conduction patterns. The implications of these findings are discussed.

The modulation of lymphocyte functions by molecules secreted by macrophages. I. Description and partial biochemical analysis

Culture fluids of peritoneal exudate cells rich in macrophages stimulated DNA synthesis of thymocytes and, to lesser extent, of spleen cells. We also investigated the effects of culture fluids from macrophages on the in vitro response to a hapten-carrier protein (fluorescein-menocyanin) using spleen cells from immune mice. Macrophage culture fluids contained an activity that increased the plaque-forming cell response of both IgG and IgM class. This increase was observed in the absence of any added hapten protein to the culture. The helper function of T lymphocytes (as evidenced by challenging with the hapten on the homologous carrier) was also increased by the macrophage culture fluid. However, this enhancement was best observed in conditions of relatively low T-cell activity. Also, the macrophage fluid allowed spleen cells of nude athymic mice to make a plaque-forming cell response to sheep red blood cells of both the IgM and IgG class. The macrophage was the cell source of the stimulatory molecule since it was generated only in cultures of macrophages devoid of significant number of lymphocytes. Stimulatory activity was not found in cultures of lymphocytes, mouse embryo cells, or 3T3 cells. The thymocyte stimulatory molecule did not contain H-2 antigens, was resistant to diisopropylfluorophosphate treatment, eluted from Sephadex with a size ranging from 15,000 to 21,000 daltons, and was sensitive to chymotrypsin and pepsin.

An inhibitor of cell proliferation released by cultures of macrophages

Culture fluids from mouse peritoneal exudate cells inhibited [(3)H]thymidine incorporation by, and proliferation of, EL-4 leukemia cells, 3T3 cells, and mitogen-stimulated spleen lymphocytes. Inhibited EL-4 leukemia cells recovered their normal proliferative capacity when washed and incubated in normal medium. The inhibitory activity resided in a low-molecular-weight substance that could be absorbed by incubation with the tumor cells. This substance was dialyzable and resistant to tryptic digestion and phosphodiesterase treatment. The mononuclear phagocytes in the peritoneal exudate seemed to be the source of the inhibitor. The inhibitory material was found in the same amounts in exudates of normal mice or mice injected with peptone or infected with Listeria monocytogenes; spleen cells adherent to plastic released the inhibitor but in lesser amount. We suggest that this inhibitor may contribute to the deleterious effects found when various cells, including neoplastic ones, are cultured in the presence of macrophages.